Insulation to block airflow and frozen pipes

Our house has just been rebuilt after a fire. The original frame including an addition that existed before the fire has mostly been rebuilt as it was. The wall between the original house frame and the addition was so charred it had to be removed and replaced, so we had a laminated beam put in and re-positioned the wall when it was rebuilt for a better kitchen.

The first floor addition area has R30 insulation and bubble foil radiant barrier in the ceiling below the attic space. The room is toasty warm, and the attic space is really freezing cold, as it should be.

The laminated beam creates a wall between the attic where first floor extends further out than the second floor in the back of the house and the space between floors. There is also an area where a concrete block wall also cuts off the addition attic space from between the floors. However, there is a space of four joist bays between the end of the laminated beam and the end of a second floor laundry room where it appears that the joists in the first floor ceiling extend beyond the end of the second floor space into the attic space. There is nothing but the batt insulation to block air from the attic space from entering between floors.

The picture below was taken above this open space. The OSB sheeting is the exterior wall of the second floor laundry room. The joist bay with the insulation sticking up the tallest is the bay where about a foot back further back just under the laundry room are the pipes for the washing machine supply. You can see the top of the laminated beam in the background just left of the center of the frame. There is a tiny insulated gap for wires to run with continued sheeting above it.

The laundry room has waterproof vinyl floor tile. Water spills in the laundry room flow into the space between the wall and floor and then over the edge into the pictured open joist bays and through the insulation and/or run along the ledge to pour down into the kitchen. The contractor is supposed to put vinyl base edging into the laundry room and seal it to the floor, so spills are trapped to mop up. I did not want a drain in the laundry room floor as the trap would probably go dry from evaporation under normal use.

The darling wife has managed to come up with some creative ways to spill loads of water in the laundry room. She would connect the washing machine to use it for a load when it was disconnected for work on the pipes, such as when they froze. Let's just say that it was trial and error for her to figure out how to connect those hoses.

There also was a screw-up where the either the one of the construction crew or the siding contractor installed a dryer vent on the outside where it was cut through the siding but not into the laundry room. We had a proper vent installed in the correct location. However, a set of comical errors on the part of the contractor's employees unloading and loading his truck when he tried to bring over the replacement siding piece ended up leaving the hole in the siding with just tape covering it during some heavy rains. As a result, there is some water damage in the ceiling below those open bays. The siding has been repaired since then.

The batt insulation in those open stud bays is now quite wet and cold.

Last week the laundry washer supply pipes froze. We cut the wall to check the pipes in the laundry room, and there was a freezing wind shooting out of the holes in the floor where the pipes came out. They were frozen by the elbows in the second floor space just about a foot inside from the exterior sheeting seen in the picture. I let the pipes conduct heat from the room with the valves open and supply hoses in the sink until they unfroze. Fortunately, the pipes did not burst. It turns out the wet R30 batt insulation is not enough to stop the airflow from the super cold attic space into the second floor space. The extreme temperature difference increases the airflow.

Just to add to it, when water spills into the open joist bays, it pours down into a smoke detector in the first floor ceiling. Smoke detectors in every room of the house are hardwired into AC power with a battery backup and are networked. If one goes off, they all go off. The water triggers the detector which sets them all off. The children wake up in a panic. This is not good for them when we have just moved back into our house after they had to previously jump out the window of a house in flames in the middle of the night.

The frozen pipes adventure led us down the detective path to access the attic space, find this all out and put it together.

The contractor is committed to making this right. The only question is how to make sure it is done properly.

The easy solution would be to replace the wet insulation from the top, and then cap the open bays up to the ledger/header cross beam (on the right side of the picture) to block the airflow from the attic space to the second floor space. The wires moving though those bays in the picture make that impractical. Can wood sheeting go in between the joists to make a wall extending into the floor space from where the exterior wall of the second floor is? That may not be possible to reach into or secure properly.

Is there some type of waterproof insulation dense enough to stop airflow that will give at least an R30 rating to use instead of fiberglass batt in those stud bays that would solve the problem? Would the Roxul rock wool batt insulation do the trick there?

Thanks.
---Hillel

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You have probably given us a lot more information than we need and it is confusing the issue. IF you need "waterproof insualation", then you need to STOP the source of the moisture. As far as the piping is concerned, if it is the outside wall, which it appears to be because of the insulation, NOTHING will prevent it from freezing if the cold persists long enough and the washer is not used frequently to replenish "warmer water" in the pipes. This would be a worse case if the piping is enclosed in the insulation rather than being close to the finished wall and being exposed to the heat from the room coming through the wall.

The lack of blocking of the joist bays on a cantilevered floor is a common "thermal bypass" construction error.

No fiber insulation is going to be sufficiently air-retardent to block the air currents completely. Cutting in chunks of rigid foam insulation as air-blocks between joists and foam-sealing the edges/holes, then BLOWING fiber insulation into the cavity can be part of the solution, but I'd need a better picture than the 10,000 rambling words and a single snapshot above to figure out what does/doesn't work from both a thermal and moisture performance point of view. (Are those floor joists or rafters at the top?)

The batts as-installed in the picture are an abyssmal joke even without the thermal bypass air leak issues, since they don't fill the joist spaces and have huge gaps, compressions and voids (apparently to accommodate the wiring?)

Any wiring/plumbing penetrations need to be air-sealed at the gypsum too, or you'll have warm humid conditioned space air adding moisture to the mold food (aka "OSB") and other wood all winter.

If the plumbing and washer are inside the major-R of the insulation everywhere you'd be protected from freeze-up issues if you can stop the thermal bypass air currents. If you can't figure it out yourself, air-seal what you can and find an insulation contractor who offers air-sealing as a service. All insulation contractors SHOULD offer that as part of ANY insulation installation, IMHO, since low density fiber insulation in a non-air-tight cavity is just an air filter, not insulation, and SURELY isn't an air-retarder. Snug-fitting high-density "cathedral ceiling" batts can be sufficiently air retardent to work from a thermal point of view, but never from a moisture transfer point of view.

Figure out what is supposed to be the inside & outside of the house from a pressure & insulation point of view, and make sure to properly air-block where joist bays cross the boundary. Seal it up the best you can, then have an air sealing contractor blower-door test the house under both positive & negative pressure to find out where the other big holes are. Clearly the air leakage between attic and this area via the joist bays bypassing I-beam through to the poorly installed insulation and unsealed stud bays is just one major path, but it's just the most-obvious part. The lack of any type of caulking/foam where the OSB meets other framing is also huge leak, but may be of lesser consequence.

Don't worry about making the house "too tight"- that's a damned-near impossibility from where you're starting out. Getting it sufficiently air tight that the insulation can perform to at least half it's rated R might even be difficult. You may be able to blow cellulose over those poorly installed batts & wiring up to a few inches over the joist tops and gain significant air retardency, since cellulose is many times more air retardent than R30 batts, and blown insulation will fill in all of the gaps, but it's no substitute for air sealing, rather an "in addition to" measure to bring thermal performance up to snuff.

The lack of blocking of the joist bays on a cantilevered floor is a common "thermal bypass" construction error.

No fiber insulation is going to be sufficiently air-retardent to block the air currents completely. Cutting in chunks of rigid foam insulation as air-blocks between joists and foam-sealing the edges/holes, then BLOWING fiber insulation into the cavity can be part of the solution, but I'd need a better picture than the 10,000 rambling words and a single snapshot above to figure out what does/doesn't work from both a thermal and moisture performance point of view. (Are those floor joists or rafters at the top?)

Click to expand...

Sorry about all that rambling. This is the sort of thing that we probably would not have noticed for years if not for all the different things going wrong at the same time.

Just to clear up, yes those are rafters in the top of the picture. The picture was taken inside the attic space over the first floor outside the end of the second floor living space. I don't know if it is physically possible to go in there and seal every crack with foam. I could just barely reach my hand inside to take the picture.

The plumbing for the second floor laundry room is in the insulated space between the floors that is inside the exposed joist bay. It was freezing from air blowing in over the installed batt insulation. Having the batt soaked with water from spills also contributed.

Yes, we are addressing sealing up the laundry room properly so that spills should not be getting out. There are no leaks in the plumbing, just foolish spills (i.e., user error). The siding issue that caused a leak was also corrected.

If you try to blow insulation into the area of the picture you need to maintain 2" clearance between the roof deck and fiber to meet code, which may be a VERY iffy proposition. But the pink stuff as-installed is doing basically squat. A spray foam installer who is a true artist with a foam gun can probably put a lumpy 4-5" on top of the pink stuff and wiring without fully blocking the rafter bays and bring down the size of the thermal bypass hole by a LOT and give it some R value there.

If the other side of the OSB panel is attic floor or a finished conditioned space floor, it's usually possible for cellulose installers to drill a single 1.25" hole per joist bag right at the wall, insert a feed-bag and dense-pack the feed bag full of cellulose to 3.5-4lbs/cubic foot density, which is about as close to fully air-tight as you can get without ripping it all open.

Blowing 3"-5" of cellulose over batt insulation improves it's air retardency by quite a bit, if that's even possible. I'm still not totally clear on where things are relative to one another, but you have some pretty classic thermal bypass air currents to fix- the key is to identify and fix as many of them as possible in the first go, before bringing in the pros with infra red cameras and blower doors- that way you get the best/most use out of their services. It's difficult to even find the smaller yet still significant leaks when the barn door is standing open. More here.